Axial fan housing configured to redirect the recirculating flow of leak air in the main flow direction

ABSTRACT

The invention also concerns a corresponding ventilation device (5) and a corresponding cooling module

The field of the present invention is that of motor vehicles and more particularly that of the circulation of air for cooling equipment of the vehicle, in particular its engine. The invention concerns in particular a ventilation device support, a corresponding ventilation device and a corresponding cooling module.

Vehicles need to evacuate the heat generated by the operation of their internal combustion engine and to this end are equipped with heat exchangers, in particular cooling radiators, that are placed at the front of the vehicle and through which external air passes. To force the circulation of that air through the exchanger or exchangers, a ventilation device is placed on the upstream or downstream side of the latter, upstream or downstream in the present document being referred to the direction of aspiration of air by the ventilation device.

The assembly formed by the heat exchanger or exchangers and the ventilation device is termed a cooling module.

The ventilation device includes at least one impeller that is used to force the circulation of air. In a known configuration the impeller is disposed between the heat exchanger, or a set of heat exchangers, and the engine block to be cooled in a globally axial alignment. The impeller is characterized by the flow of air that it produces and that is used to force thermal exchanges between the heat exchanger and the surrounding air. The impeller produces an axial flow. It includes blades connected by their root to a central hub and generally fastened together at their tip by a peripheral shroud also termed a rotating shroud. The ventilation device therefore creates a flow of air that is aspirated on the upstream side through the exchangers and the air is forced to flow axially in the downstream direction in the engine compartment.

The ventilation device, also termed a motorized fan, generally includes a nozzle or base, for example of parallelepiped shape, having at least one orifice or a cylindrical cut-out receiving the impeller. This nozzle attaches the ventilation device, in particular to the cooling radiator or the chassis of the vehicle, and also forms a support for the electric motor driving the impeller. It carries the shaft about which the impeller rotates.

To enable the rotation of the impeller, the latter is received in the orifice of the nozzle with a clearance of the order a few millimeters, generally 3 mm to 5 mm. It proves that when the ventilation device is operating air from the downstream side of the impeller can return to the upstream side thereof by flowing outside the peripheral shroud, between the peripheral shroud and the nozzle. This air that recirculates to the upstream side of the impeller creates a so-called recirculating flow of air. On arriving on the upstream side of the impeller, the recirculating air is again drawn into the main flow of air generated by the impeller and its relatively intense radial flow comes to disturb the main upstream to downstream flow of air. This turbulence can impact up to 30% of the span of the blades of the impeller, and generates noise. Because the flow of air is no longer homogeneous, and the clearance between the peripheral shroud and the nozzle generates losses, the effectiveness of the ventilation device is reduced.

According to one known solution, the nozzle has at the periphery of the orifice to receive the impeller a curved portion covering the upstream edge of the peripheral shroud in such a way as to guide the recirculating flow of air coming from the downstream side. However, with this solution, the flow of air recirculating from the downstream side outside the peripheral shroud still has a tangential component that comes to disturb the main flow of air.

The present invention proposes to remedy at least in part the disadvantages referred to above by proposing an improved ventilation device support enabling the reduction in performance of the ventilation device to be avoided.

To this end the invention consists in a support for a ventilation device of a motor vehicle including an impeller configured to be rotated about a rotation axis in such a way as to generate a flow of air, the support including a nozzle:

-   -   having an orifice configured to receive the impeller, and     -   having at the periphery of the orifice an internal wall         configured at least to partially cover one side of a peripheral         shroud of the impeller.

According to the invention, the nozzle further includes on its internal wall an air guide shaped so as to direct a flow of air flowing between the peripheral shroud and the internal wall, termed the recirculating air flow, in the direction of flow of the flow of air generated by the impeller.

The air guide therefore enables the speed of the tangential recirculating flow of air to be reduced so as not to disturb the main flow of air.

Said support may further have one or more of the following features, separately or in combination:

-   -   the internal wall of the nozzle has an axial section configured         to extend around the peripheral shroud and a curved section         extending toward the interior of the orifice so as to cover         radially the end of said shroud when the impeller is assembled         into the nozzle;     -   the curved section is configured to cover radially the upstream         edge of said shroud in the direction of flow of the flow of air         generated by the impeller;     -   the air guide is formed on the axial section;     -   the air guide is formed on the curved section;     -   the air guide is produced by at least one rib;     -   the air guide is produced by at least one protuberance;     -   the air guide is produced by at least one pin;     -   the air guide is produced by at least one stud;     -   the air guide is produced by at least one hollow;     -   the air guide is produced by a plurality of ribs extending over         the internal wall of the nozzle;     -   the air guide is produced by a peripheral rib extending over the         internal wall of the nozzle and having a substantially         crenellated shape.

The invention also concerns a ventilation device including an impeller configured to be rotated about a rotation axis in such a way as to generate a flow of air, the impeller including a plurality of blades and a peripheral shroud connecting the tips of the blades. According to the invention, said device further includes a support as defined above including a nozzle having an orifice in which the impeller is positioned and having at the periphery of the orifice an internal wall covering at least partly one side of the peripheral shroud. The nozzle further includes on its internal wall an air guide shaped in such a way as to guide a flow of air flowing between the peripheral shroud and the internal wall in the direction of flow of the flow of air generated by the impeller.

Said device may further have one or more of the following features, separately or in combination:

-   -   the peripheral shroud has a substantially cylindrical shape;     -   the nozzle includes a curved section of substantially “U” shape;     -   the curved section delimits a groove inside which the peripheral         shroud of the impeller extends;     -   the curved section delimits a groove and the peripheral shroud         of the impeller is axially set back relative to the groove.

The invention also relates to a cooling module for motor vehicles equipped with a ventilation device as described above.

According to one aspect of the invention said module includes a heat exchanger located on the path of at a part of the flow of air generated by the impeller.

Other features and advantages of the invention will become more clearly apparent on reading the following description given by way of nonlimiting illustrative example and from the appended drawings, in which:

FIG. 1 is a simplified diagrammatic view of a cooling module for an engine block of a motor vehicle,

FIG. 2 is a perspective view showing a ventilation device of the cooling module from FIG. 1,

FIG. 3 is a front view showing part of the ventilation device from FIG. 2,

FIG. 4 is a sectional view showing part of a nozzle receiving an impeller of the ventilation device from FIG. 3,

FIG. 5 is a first partial perspective view showing one embodiment of a peripheral shroud of the impeller, the nozzle and an air guide formed on an internal wall of the nozzle comprising a plurality of “L” shape ribs,

FIG. 6 is a second partial perspective view showing the embodiment from FIG. 5 of the peripheral shroud of the impeller, the nozzle and the air guide,

FIGS. 7 to 11 are partial perspective views showing different embodiments of the peripheral shroud of the impeller, the nozzle and the air guide comprising a plurality of ribs formed on an axial section of the internal wall of the nozzle,

FIG. 12 is a partial perspective view showing one embodiment of a peripheral shroud of the impeller, the nozzle and an air guide formed on an internal wall of the nozzle comprising a plurality of ribs formed on a curved section of the internal wall of the nozzle,

FIG. 13 is a sectional view showing part of a nozzle receiving an impeller and having a peripheral rib on its internal wall, and

FIG. 14 is a sectional view showing part of the nozzle receiving an impeller and having a peripheral rib formed on an axial section and a curved section of the internal wall of the nozzle.

In these figures identical elements bear the same references.

The following embodiments are examples. Although the description refers to one or more embodiments, that does not necessarily mean that each reference concerns the same embodiment or that the features apply only to only one embodiment. Single features of different embodiments may equally be combined or interchanged to produce other embodiments.

In the description, some elements may be indexed, for example first element or second element. In this case, this is merely indexing to differentiate and to designate elements that are similar but not identical. This indexing does not imply any priority of one element relative to another and such designations may easily be interchanged without departing from the scope of the present description. Nor does this indexing imply an order in time.

There has been represented diagrammatically in FIG. 1 a cooling module 1 for a motor vehicle engine block 3. The cooling module 1 includes in particular a ventilation device 5 and at least one heat exchanger 7 such as a cooling radiator 7.

According to the embodiment shown in FIG. 1, the ventilation device 5 is placed between the cooling radiator 7 and the engine block 3. Of course, the cooling device 5 may be arranged either in front of or behind the cooling radiator 7.

The invention is more particularly directed to the ventilation device 5. The ventilation device 5 includes an impeller 9 and a support 10 including a base or nozzle 11, also termed an armature, seen better in FIG. 2 and represented in part in FIGS. 3 to 13.

The impeller 9 is rotatable about a rotation axis A. In the remainder of the description the terms “axial”, “radial” and “tangential” are relative to the rotation axis A of the impeller 9.

Referring again to FIG. 1, the engine block 3, the impeller 9 and the cooling radiator 7 are substantially aligned in the axial direction.

When the impeller 9 is configured to be rotated by an electric motor 12 represented diagrammatically in FIG. 2. The rotating impeller 9 moves the flow of air and drives it through the cooling radiator 7. To this end the heat exchanger 7 is situated on the path of at least a part of the flow of air generated by the impeller 9. The flow of air flows in an aspiration direction or flow direction substantially oriented from the cooling radiator 7 to the engine block 3, as symbolized by the arrow F in FIG. 1. In the remainder of the description, by “upstream” and “downstream” are meant the directions associated with the flow direction F of the flow of air generated by the impeller 9.

The impeller 9 is for example made of injection molded plastic.

As can be seen better in FIGS. 3 and 4 this impeller 9 includes:

-   -   a central hub 13, also termed the “bowl”,     -   a plurality of blades 15 with first ends 15 a, termed blade         roots, around the central hub 13 that extend radially from the         central hub 13, and     -   a peripheral shroud 17 to which are attached the second ends 15         b of the blades 15, termed blade tips 15 b.

The tips 15 b of the blades 15 of the impeller 9 are therefore attached to one another by the peripheral shroud 17. This enables reduction of the risks of the blades 15 floating when the ventilation device 5 is operating. The peripheral shroud 17 connecting the blades 15 of the impeller 9 is also termed a rotating shroud.

According to the embodiments shown the peripheral shroud 17 has a substantially cylindrical shape that extends along the rotation axis A of the impeller 9. Of course, any other shape may be envisaged.

The invention is more particularly directed to the support 10 for the ventilation device 5 including the nozzle 11, represented diagrammatically in FIG. 2.

The nozzle 11 has the function of capturing air and guiding air toward the impeller 9. The nozzle 11 also has a mechanical support function for all of the components of the ventilation device 5.

In known manner, the nozzle 11 may have a substantially parallelepiped shape extending substantially parallel to the cooling radiator 7 presented diagrammatically in FIG. 1.

The nozzle 11 may in particular carry the electric motor 12 (FIG. 2) intended to drive the impeller 9. To this end the nozzle 11 may include a central cap 18 in which the electric motor 12 is intended to be positioned. The central cap 18 is fixed.

The nozzle 11 also includes an axial cylindrical cut-out or orifice 19 allowing passage of the ventilation air. The orifice 19 is formed around the central cap 18. The impeller 9 is intended to be disposed inside the orifice 19 of the nozzle 11. The impeller 9 is therefore able to rotate within the orifice 19 formed in the nozzle 11.

The nozzle 11 further includes retaining arms 20. These are arms extending radially across the orifice 19 and are attached to the periphery of the orifice 19 of the nozzle 11. The retaining arms 20 join at the center to the central cap 18. Via the central cap 18 the retaining arms 20 carry the electric motor 12 adapted to drive the central hub 13 of the impeller 9.

Referring to FIGS. 4 to 13, the nozzle 11 further includes an internal wall 21 in which is formed a recess 23 forming a housing for the peripheral shroud 17. The recess 23 is formed on the internal wall 21 at the periphery of the orifice 19.

The recess 23 is shaped so that the internal wall 21 of the nozzle 11 covers the upstream side of the peripheral shroud 17.

According to the example show the recess 23 formed in the internal wall 21 is such that the internal wall 21 includes an axial section 25, here of substantially cylindrical shape about the rotation axis A of the impeller 9, and this axial section 25 is configured to extend around the peripheral shroud 17. It is in particular a downstream section 25 with reference to the aspiration direction or flow direction F of the flow of air. The axial section 25 is extended on the upstream side by a curved section 27. The curved section 27 therefore forms an upstream section 27 with reference to the aspiration direction or the flow direction F of the flow of air. The curved section 27 is intended to cover, to be more precise radially to cover, the upstream side of the peripheral shroud 17 when the impeller 9 is assembled into the nozzle 11. The curved section 27 therefore extends toward the interior of the orifice 19.

Thus in cross section the internal wall 21 has substantially the shape of a hook, with the curved section 27 having in cross section a substantially “U” shape having two branches extending substantially axially and a base connecting the two branches and forming the cover of the peripheral shroud 17. The end of the curved section 27 therefore extends the base or part that covers the peripheral shroud 17 by extending axially in the direction of the downstream side of the interior of the peripheral shroud 17.

Of course, the invention is not limited to the rounded shape of the curved section 27 shown and any other shape may be envisaged.

In other words, in this example the recess 23 is formed by a first part 23 a of substantially cylindrical shape about the rotation axis A of the impeller 9 and a second part 23 b of substantially toroidal shape that extends the cylindrical part 23 a in the upstream direction in such a way as to form a groove 23 b. The two parts 23 a and 23 b of the recess 23 are diagrammatically delimited by an axis B in dashed line in FIG. 4. The curved section 27 therefore delimits the groove 23 b.

The flow of air, also termed the clearance flow or recirculating flow of air, that flows outside the peripheral shroud 17 from the downstream side of the impeller 9 to the upstream side is therefore redirected by the curved section 27 of the internal wall 21 of the nozzle 11. The recirculating flow of air flows between the peripheral shroud 17 and the internal wall 21. The peripheral shroud 17 and the internal wall 21 of the nozzle 11 therefore form a channel 28 for redirecting the flow of air recirculating from the downstream side to the upstream side.

The axial section 25 of the internal wall 21 of the nozzle 11 can extend axially over a height h₂₅ substantially similar to the height h₁₇ of the peripheral shroud 17, as shown in the examples from FIGS. 4 to 8 and 12, 13. To the contrary, there may be a height difference between the axial section 25 and the peripheral shroud 17. According to the example shown in FIGS. 9 to 11, the peripheral shroud 17 extends to a height h₁₇ lower than the height h₂₅ of the axial section 25 of the internal wall 21 of the nozzle 11. The height difference is left for the person skilled in the art to assess according to the application.

The inside diameter of the axial section 25 of cylindrical shape of the internal wall 21 of the nozzle 11, that is to say at the level of the first part 23 a of the recess 23 (see FIG. 4), is therefore greater than the diameter of the peripheral shroud 17. The size of the radial clearance between the cylindrical axial section 25 and the peripheral shroud 17 may be adapted by the person skilled in the art according to what is required.

The inside diameter of the internal wall 21 of the nozzle 11 at the level of the curved section 27 is for its part less than the diameter of the peripheral shroud 17.

The curved section 27 delimiting the groove 23 b may extend radially relative to the peripheral shroud 17 over a distance d, d′ that may be modified (see FIGS. 6 and 7). In the example from FIG. 6 the radial distance d between the peripheral shroud 17 and the end of the curved section 27 is therefore relatively small. To the contrary, in the example from FIG. 7 the radial distance d′ between the peripheral shroud 17 and the end of the curved section 27 is greater.

When the impeller 9 is received in the orifice 19 of the nozzle 11 the blades 15 of the impeller 9 therefore extend radially between the central hub 13 and the internal wall 21 of the nozzle 11, the peripheral shroud 17 of the impeller 9 extends inside the recess 23 of the internal wall 21 of the nozzle 11, and the curved section 27 of the internal wall 21 of the nozzle 11 covers the upstream side of the peripheral shroud 17.

In the example shown in FIG. 4 the upstream side of the peripheral shroud 17 extends inside the groove 23 b. In other words, the free extremity of the hook or curved section 27 extends in part inside the peripheral shroud 17 of the impeller 9.

Alternatively, there may be an axial offset (not shown in the figures) between the upstream side of the peripheral shroud 17 and the curved section 27 of the nozzle 11. In other words, according to this alternative, the upstream side of the peripheral shroud 17 does not extend inside the groove 23 b but is axially set back relative to the groove 23, that is to say below the groove 23 b in the aspiration direction or flow direction F of the flow of air. Likewise, the free end of the hook or curved section 27 does not extend inside the cylinder delimited by the peripheral shroud 17 of the impeller 9.

In a complementary way, the nozzle 11 includes on its internal surface an air guide 29 for directing the recirculating flow of air in the flow direction of the flow of air generated by the impeller 9, that is to say a substantially axial flow toward the downstream side of the impeller 9, as symbolized by the arrow F′ in FIG. 4, so as to limit the tangential or radial component of the recirculating flow of air, which would otherwise disturb the flow of the flow of air from the upstream side to the downstream side as shown by the arrow F. In other words, the air guide 29 is shaped or configured in such a way as to limit the tangential speed of the recirculating flow of air.

The air guide 29 is preferably shaped in such a way as to force redirection of the recirculating flow of air at least in part within the thickness of the boundary layer c_(l) of the peripheral shroud 17 at the level of the blade tips 15 b. The recirculating flow of air comes to be mixed at least in part with the boundary layer c_(l) of the peripheral shroud 17. This makes it possible to increase the flow speed in the boundary layer c_(l) and to limit its extent.

The air guide 29 may moreover be formed on the axial section 25 and/or on the curved section 27 of the internal wall 21 of the nozzle 11.

In particular, referring to FIGS. 5 to 13, the nozzle 11 includes to this end a predefined number of ribs 31 on the internal wall 21, the rib or ribs 31 forming the air guide 29. The number of ribs 31 is adapted as required. Likewise, the pitch between the rubs 31 may be adapted by the person skilled in the art.

The ribs 31 are arranged in such a way as to force the clearance flow axially. In fact, the presence of the ribs 31 in the redirection channel 28 has the consequence of limiting or breaking up the tangential component of the recirculating air.

The ribs 31 are advantageously sized in such a way as to limit the recirculation of the recirculating air at the level of the blade tips 15 b.

The ribs 31 may be arranged on the axial section 25 and extended onto the interior of the curved section 27, that is to say on the side intended to face the upstream side of the peripheral shroud 17, as shown in FIGS. 5 and 6.

The ribs 31 may instead be arranged only on the axial section 25, as shown in FIGS. 7 to 11.

According to a further variant the ribs 31 may be arranged only on the interior of the curved section 27 or in other words inside the groove formed by the second part 23 b of the recess 23, as shown in FIGS. 12 and 13.

The ribs 31 may extend axially and/or radially.

The ribs 31 are shaped in such a way as to follow the contour of the internal wall 21 of the nozzle 11. The shape of the ribs 31 may also be adapted as required.

The examples from FIGS. 4 to 13 are described in more detail hereinafter.

By way of example, as shown in FIGS. 5 and 6, a plurality of ribs 31 may extend both in the bottom of the groove 23 b, that is to say on the interior part of the curved section 27, and on the axial section 25, here of substantially cylindrical shape. To this end the ribs 31 have a substantially “L” shape. The parts of the ribs 31 arranged in the bottom of the groove 23 b extend radially and the parts of the ribs 31 arranged on the cylindrical axial section 25 extend axially. Moreover, the parts of the ribs 31 arranged in the bottom of the groove 23 b have a contour that follows the curved shape of the upstream section 27, in this example a substantially rounded contour.

Of course, the size of these ribs 31 may be modified. For example, the ribs 31 may extend or not over all the height h₂₅ of the axial section 25 and over all the width of the curved section 27.

The width or depth, that is to say the radial dimension of the ribs 31, may also be modified. The thickness of the ribs 31 may also be modified.

According to the examples shown in FIGS. 7 to 11 the ribs 31 may be arranged on the axial section 25. In the example shown the ribs 31 have a tapered blade shape on the downstream side, that is to say at the level of the beginning of the return or the curvature of the curved section 27.

As before, the size of these ribs 31 may be modified. For example, the ribs 31 may extend over all of the height h₂₅ of the axial section 25 or in a variant that is not shown over a chosen portion of the axial section 25.

The width or depth, that is to say the radial dimension, of the ribs 31 may also be modified. In the examples from FIGS. 7 to 9 the ribs 31 may have a small width whereas in the examples from FIGS. 10 and 11 the ribs 31 are wider.

According to the examples from FIGS. 12 and 13 the ribs 31 are this time arranged only in the bottom of the groove 23 b delimited by the curved section 27 of the nozzle 11.

In the example shown in FIG. 12 the ribs 31 extend radially in the bottom of the groove 23 b. The ribs 31 have for example a respective substantially half-moon shape firstly along the contour of the curved section 27 and secondly along the contour of the upstream side of the peripheral shroud 17. As before, the number, the shape and the size of these ribs 31 may be modified.

In the example shown in FIG. 13 a peripheral rib 31 is arranged in the bottom of the groove 23 b and is notched or has a substantially crenellated shape with an alternation of teeth and gaps. As before, the shape and the size of this rib 31 may be modified.

Moreover, by way of nonlimiting example and referring to FIG. 14, for a rib 31 at least a part of which extends axially the radial clearance j_(r) between the peripheral shroud 17 and the axial extent of the rib 31 may be of the order of 0.5% to 2% of the diameter of the impeller 9, preferably of the order of 1% of the diameter of the impeller 9. For an impeller 9 of approximately 440 mm diameter, for example, the radial clearance j_(r) may therefore be of the order of 4.4 mm.

The radial depth p_(r) of the rib 31, to be more precise its axial extent, may be of the order of 0.5% to 2% of the diameter of the impeller 9, preferably of the order of 1% of the diameter of the impeller 9. For example, the radial depth p_(r) is of the order of 4.4 mm for an impeller 9 of approximately 440 mm diameter.

Moreover, for a rib 31 at least a part of which extends radially the axial clearance j_(a) between the peripheral shroud 17 and the radial extent of the rib 31 may be of the order of 0.5% to 4% of the diameter of the impeller 9, preferably of the order of 2% of the diameter of the impeller 9. For example, for an impeller of approximately 440 mm diameter the axial clearance j_(a) may be of the order of 8.8 mm.

The axial depth p_(a) of the rib 31, to be more precise its radial extent, may be of the order of 0.5% to 4% of the diameter of the impeller 9, preferably of the order of 2% of the diameter of the impeller 9. For example, the axial depth p_(a) is of the order of 8.8 mm for an impeller 9 of approximately 440 mm diameter.

In the example from FIG. 14 each rib 31 extends both radially over the interior part of the curved section 27 and axially over the axial section 25, having a substantially “L” shape and the axial clearance j_(a) and the radial clearance j_(r) defined relative to the peripheral shroud 17.

In addition or alternatively to the various examples described above, there may be provided in the recirculation channel 28 (see FIGS. 4 to 13), that is to say in the bottom of the groove 23 b delimited by the curved section 27 of the nozzle 11 and/or on the axial section 25, a surface having asperities (not shown in the figures) such as a plurality of recesses, protuberances, studs or pins making it possible to limit the tangential speed of the flow of air circulating outside the peripheral shroud 17.

Thus the internal surface of the nozzle 11 is adapted in a particular way to ensure aerodynamic guiding of the recirculating flow of air coming from the downstream side and recirculating outside the peripheral shroud 17. The flow of air retuning from the downstream side of the impeller 9 to the upstream side is therefore guided by the ribs 31 so that it flows substantially axially, in the flow direction F of the flow of air generated by the impeller 9, at least in part within the thickness of the boundary layer c_(l) of the peripheral shroud 17.

The recirculating flow of air is then separated from the main flow of air circulating in the upstream to downstream direction. In fact, this flow of air does not disturb the upstream to downstream flow of air in the direction of the arrow F. This therefore eliminates the turbulence that would otherwise be associated with the mixing of the clearance flow with the upstream flow, which makes possible a significant variation of pressure and of output. 

1. A support for a ventilation device of a motor vehicle, the ventilation device including an impeller configured to be rotated about a rotation axis in such a way as to generate a flow of air, the support comprising: a nozzle having: an orifice configured to receive the impeller at the periphery of the orifice, an internal wall configured to cover at least partially one side of a peripheral shroud of the impeller, and on the internal wall, an air guide shaped so as to direct a flow of air flowing between the peripheral shroud and the internal wall, in the direction of flow of the flow of air generated by the impeller.
 2. The support as claimed in claim 1, wherein the internal wall of the nozzle has an axial section configured to extend around the peripheral shroud and a curved section extending toward the interior of the orifice so as to cover radially the end of said shroud when the impeller is assembled into the nozzle.
 3. The support as claimed in claim 2, wherein the air guide is formed on the axial section.
 4. The support as claimed in claim 2, in which the air guide is formed on the curved section.
 5. The support as claimed in claim 1, wherein the air guide is produced by at least one of the following elements: ribs, protuberances, pins, studs and recesses.
 6. A ventilation device for motor vehicles, said device comprising: an impeller configured to be rotated about a rotation axis in such a manner as to generate a flow of air, the impeller including a plurality of blades and a peripheral shroud connecting the tips of the blades; and a support including: a nozzle having an orifice configured to receive the impeller, at the periphery of the orifice, an internal wall configured to cover at least partially one side of a peripheral shroud of the impeller, and on the internal wall, an air guide shaped so as to direct a flow of air flowing between the peripheral shroud and the internal wall, in the direction of flow of the flow of air generated by the impeller.
 7. The device as claimed in claim 6, wherein the internal wall of the nozzle of the support has an axial section configured to extend around the peripheral shroud and a curved section extending toward the interior of the orifice so as to cover radially the end of said shroud when the impeller is assembled into the nozzle, and wherein the peripheral shroud has a substantially cylindrical shape and the curved section has a substantially “U” shape.
 8. The device as claimed in claim 6, wherein the internal wall of the nozzle of the support has an axial section configured to extend around the peripheral shroud and a curved section extending toward the interior of the orifice so as to cover radially the end of said shroud when the impeller is assembled into the nozzle, and wherein the curved section delimits a groove inside which the peripheral shroud of the impeller extends.
 9. The device as claimed in claim 6, wherein the internal wall of the nozzle of the support has an axial section configured to extend around the peripheral shroud and a curved section extending toward the interior of the orifice so as to cover radially the end of said shroud when the impeller is assembled into the nozzle, and wherein the curved section delimits a groove, and in which the peripheral shroud of the impeller is set back axially relative to the groove.
 10. A cooling module for motor vehicles, including: a ventilation device comprising: an impeller having a plurality of blades and a peripheral shroud connecting the tips of the blades, the impeller being configured to be rotated about a rotation axis so as to generate a flow of air, and a support including: a nozzle having an orifice configured to receive the impeller, at the periphery of the orifice, an internal wall configured to cover at least partially one side of a peripheral shroud of the impeller, and on the internal wall, an air guide shaped so as to direct a flow of air flowing between the peripheral shroud and the internal wall, in the direction of flow of the flow of air generated by the impeller; and a heat exchanger located on the path of at least part of the air flow generated by the impeller. 